Cut and paste from the following site
http://www.dft.gov.uk/vosa/repository/08%201246.pdfI forwarded your request to my colleagues who have responsibility for the MOT, and
they have informed me that the MOT Inspection Manual which you have quoted is
that for motorcycles, which has subtle differences from that for motor vehicles which
states:-
With the engine running assess subjectively the effectiveness of the silencer
in reducing exhaust noise to a level considered to be average for the vehicle,
and the Reason for Rejection (RfR) is; a silencer in such condition, or of such
a type, that the noise emitted from the vehicle is clearly unreasonably above
the level expected from a similar vehicle with a silencer in average condition.
It is intended to make amendments to this part of the manual in due course. The
instructions will include an instruction to assess the exhaust noise with the engine
being revved, as currently it is assessed at idle, also to include a reference to a
standard silencer in the Reason for Rejection, as in the Motorcycle Manual. As
stated in the Method of Inspection wording, the test is subjective, and therefore relies
on the tester s judgement. MOT testing stations are not required (or permitted) to
use noise meters assess the levels of exhaust noise. However, as you intimate in
your e-mail, an MOT is issued to a vehicle and only confirms that it met the minimum
standard required at the time of test. Therefore, whilst it is a big job, there is
nothing to stop a person swapping exhaust systems purely to pass a test, and then
changing it back afterwards.
Exhaust noise limits are specified in the Road Vehicles (Construction & Use)
Regulations 1986 as amended and the limits vary depending on the vehicle age and
type. The user of a vehicle that is in contravention of these regulations is committing
an offence, regardless of whether the excess noise is due to the exhaust condition or
type. The police are responsible for dealing with issues of this nature.
http://www.legislation.gov.uk/uksi/1986 ... view=plainI think you will find it is very much the whim of the cop who stops you, if it was a car easy any thing over 80 decibels and you in big do do's